One way to distinguish mistakes of inattention from "actual" mistakes is to leave marking the mistakes to the user. So if you get inattentive, you simply forget to mark yourself wrong.
My personal system works that way; though not for any particularly clever reason. I just have no idea how to automate the checks. I don't recommend anyone to try it unless you want to spend a few hours setting it up, but there's a screenshot in the README: https://github.com/Yorwba/alphabet-soup
Looks interesting but you should really ad a European language. I'm looking forward to learn Japanese and Mandarin once but don't feel like doing it right now and I probably am not alone. The LibreLingo author has made quite a wise decision to choose Spanish for the example language - it's the easiest and makes a lot sense for everybody to learn (given how many countries use it).
Well, I've chosen Japanese because I'm learning it. I'm not really looking for users right now, I just thought others might find some inspiration in what I'm doing.
My personal system works that way; though not for any particularly clever reason. I just have no idea how to automate the checks. I don't recommend anyone to try it unless you want to spend a few hours setting it up, but there's a screenshot in the README: https://github.com/Yorwba/alphabet-soup